1. Field of the Invention
This invention relates generally to image compression and, more particularly, to differential image compression.
2. Description of the Related Art
Transmission and handling of message data is an important function that must be carefully and efficiently performed. For example, a health care delivery system such as a hospital or medical center will receive message data of many different types. It is critical for the health of patients that message data are delivered to appropriate medical staff, with sufficient data integrity to be useful to the staff member. Message data may include image information, for example, image information from a laboratory examination such as an X-ray, CT Scan, or other medical examination procedure. The image information can be in a variety of data formats, such as JPEG formatted data, bitmap formatted data, TIFF formatted images, and the like including Raster formatted.
Representation of image information usually requires large amounts of data, making transmission and storage of image data challenging and expensive. Data compression is a useful tool for storing and transmitting large amounts of data. Data compression refers to techniques that represent data in a fashion that requires less “bits” then the original data to represent. Data compression is very useful in the storage of data because less storage space is required to store the data file. It is also very useful in transmission of the data file because fewer bits need to be transmitted to transfer the entire data file, therefore transferring more quickly and with less bandwidth.
In general, data compression techniques are divided into two broad categories, lossy compression and lossless compression. Lossy compression involves compression of a data file that results in the loss of some of the original information when the original data file is reconstructed from the compressed file. In other words, when the original data file is reconstructed from the lossy compressed file, there are differences, or errors, between the reconstructed file and the original file. A typical goal of lossy compression techniques is that the differences, or errors, in the reconstructed data file are not objectionable or detectable to the human visual response system.
Lossless compression involves compression of a data file that results in no loss of original information when the original data file is reconstructed. In other words, lossless compression techniques compress the original data file in such a way that when the data file is reconstructed from the compressed file there are no differences, or errors, between the reconstructed file and the original file.
Generally, lossy compression techniques can achieve a higher compression ratio, resulting in smaller compressed file sizes, as compared with lossless compression. A tradeoff is that there is degradation in the reconstructed data file using lossy compression while there is no degradation in the reconstructed data file using lossless compression.
Use of data compression techniques on medical image files can be beneficial in reducing both the storage and transmission of large image files. For example, digital radiology benefits from compression algorithms by reducing both storage and transmission cost of images. However, the amount of compression that can be achieved is limited by the amount of “loss” or errors, if any, that are acceptable in the reconstructed image, i.e., there may be resolution or loss specifications set by the application for the data. Because medical imagery may be critical for the health of patients it is very important to maintain the image “quality” which means that generally less compression can be tolerated and thus there is less efficient storage and transmission of the image data.
From the discussion above, it should be apparent that there is a need for a system and techniques that can improve data compression of image data files for reduced consumption of system resources while maintaining sufficient data fidelity. The present invention fulfills this need. Other problems with the prior art not described above can also be overcome using the teachings of the present invention, as would be readily apparent to one of ordinary skill in the art after reading this disclosure.